Index: trunk/src/org/openstreetmap/josm/actions/DeleteAction.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/DeleteAction.java	(revision 18755)
+++ trunk/src/org/openstreetmap/josm/actions/DeleteAction.java	(revision 18756)
@@ -24,4 +24,5 @@
 import org.openstreetmap.josm.gui.MapFrame;
 import org.openstreetmap.josm.gui.dialogs.DeleteFromRelationConfirmationDialog;
+import org.openstreetmap.josm.gui.util.GuiHelper;
 import org.openstreetmap.josm.gui.widgets.JMultilineLabel;
 import org.openstreetmap.josm.tools.Pair;
@@ -103,5 +104,5 @@
     public static boolean checkAndConfirmOutlyingDelete(Collection<? extends OsmPrimitive> primitives,
             Collection<? extends OsmPrimitive> ignore) {
-        return checkAndConfirmOutlyingOperation("delete",
+        return Boolean.TRUE.equals(GuiHelper.runInEDTAndWaitAndReturn(() -> checkAndConfirmOutlyingOperation("delete",
                 tr("Delete confirmation"),
                 tr("You are about to delete nodes which can have other referrers not yet downloaded."
@@ -114,5 +115,5 @@
                         + "This will cause problems because you don''t see the real object."
                         + "<br>" + "Do you really want to delete?"),
-                primitives, ignore);
+                primitives, ignore)));
     }